ARS Takes On Bird and Swine Influenza
Strains
Scientists are now learning more about how animals
can be hosts for flu viruses. Birds are believed to be a global reservoir of
influenza virus genes that make their way to humans. Since pigs can be infected
with both avian and human strains, they may also be a "mixing vessel"
in the transmission process. When bird influenza viruses infect pigs that
already contain a swine or human influenza virus, gene segments from each virus
can mix and a new influenza subtype virus can emerge.
The Centers for
Disease Control and Prevention (CDC) reported earlier this month that
approximately one half the expected supply of flu vaccine available in the
United States for the 2004-05 influenza season will not be available over
concerns about standards at the manufacturing plant.
The flu virus goes through mutations, so the flu
vaccine has to be reformulated each year based on the strains of flu that
previously appeared.
Humans can be infected with influenza types A, B, and
C. Influenza A and B are the most important strains. Type A affects mammals
(such as humans and pigs), as well as birds, but types B and C affect only
humans.
Oftentimes, the losses for swine and poultry producers
can be devastating. When Virginia experienced an outbreak of avian influenza
(H7N2) in 2002, for example, 4.7 million turkeys and chickens were
destroyed.
 When an avian influenza type A virus (H5N1) infected both
chickens and humans in 1997, ARS was ready to help. The Hong Kong incident
marked the first time an avian influenza virus had ever been found to transmit
directly from birds to humans. ARS scientists already had a working H5
influenza vaccine for birds at the time. The ARS
Southeast
Poultry Research Laboratory (SEPRL) in Athens, Ga., was studying a viral
strain called H5N2. This strain attacks only poultry but is related to H5N1,
the Hong Kong bird flu strain. Their research allowed them, and industry
cooperators, to provide
the Hong Kong government with the poultry vaccine.
Researchers at SEPRL want to understand why and how
mild viruses become highly pathogenic and are developing better diagnostic
tests with improved vaccines. The molecular research includes
identifying and
characterizing genes using a rapid polymerase chain reaction (PCR)
procedure, sequencing of the entire virus genome of representative isolates,
and creating molecular models.
Athens researchers are studying the behavior of the
viruses in living hosts and hope to better understand how certain strains
evolve to be so pathogenic and to develop ways to predict this potential
virulence.
The H5N1 influenza strain turned up again in early
2004 in a few people who died from bird flu in Vietnam and Thailand. The virus
killed 30 people in Asia earlier this year. Other nations in Southeast Asia
have reported fresh cases of bird flu in poultry in past weeks, months after a
mass culling campaign in which tens of millions of poultry were destroyed. The
strain has spread widely among poultry and other birds in Southeast Asia and
infected people there.
H5N1 also is known to have infected pigs as early as
last year. H5N1 has since crossed another species barrier to infect cats. Dutch
scientists have found that the virus can also spread among cats. It's not known
whether cats can transmit the virus strain to humans.
Historically, only one type of swine flu virus, H1N1,
was primarily found in pigs in the United States. That changed in 1998 when the
H3N2 strain showed up here in swine, and most recently, the H1N2 strain.
At the
National
Animal Disease Center in Ames, Iowa, scientists are working on ways to
control swine flu. Part of their research includes developing immunogens that
provoke a protective immune response when introduced into a body. They also
want to develop diagnostic reagents that can be used to detect the presence of
swine influenza in pigs.
Ames researchers in the Virus and Prion Diseases of
Livestock Research Unit and their collaborators use a process known as
reverse
genetics to create swine flu types that could one day help develop a
vaccine and stop the rapid spread of the virus.
For more information, contact the following
researchers:
David E.
Swayne, Athens, Ga.
Kelly
Lager, Ames, Iowa
Juergen
Richt, Ames, Iowa
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Research Briefs
Findings from an ARS researcher in Arkansas could be
instrumental in the development of
a year-round supply
of sunshine bass fingerlings.
Gerald
Ludwig
(870) 673-4483
ARS recently opened a new facility to study
stress indicators in
livestock. One issue the West Lafayette, Ind., laboratory will examine
involves the relationship between stress and the ability of pathogenic bacteria
to establish themselves in animals.
Donald
C. Lay, Jr.
(765) 496-3665
ARS and cooperating scientists named
a new genus of
bacteria found in swine manure after a late microbiologist.
Terence
R. Whitehead
(309) 681-6272
A gene that helps regulate feed intake and energy
expenditure in turkeys has been sequenced by ARS scientists. The gene codes for
the production of the hormone called
ghrelin.
Mark
Richards
(301) 504-8892
USDA officials and scientists hosted the
Foot and Mouth Disease
Global Research Alliance to discuss collaborative research in developing
better vaccines and antiviral agents against the virus that causes FMD.
An ARS microbiologist used
proteins from harmless
microorganisms to reduce Campylobacter and other pathogens by 99.999
percent in poultry intestines.
Norman
J. Stern
(706) 546-3516
Methods developed by ARS scientists in Texas are helping
Scottish scientists control ticks that are
spread from wildlife to game birds.
Mat
Pound
(830) 257-3566
ARS researchers developed
two new methods to
detect the presence of feed additives used to produce leaner cuts of pork and
beef.
Weilin
L. Shelver and
David
J. Smith
(701) 239-1425 [Shelver], (701) 239-1238, [Smith]
Awards
Jitender P. Dubey, a microbiologist with the ARS Parasite
Biology, Epidemiology and Systematics Laboratory in Beltsville, Md., was one of
several ARS personnel to win a "Presidential Rank Award" for 2003.
Dubey's pioneering
research into the biology and control of toxoplasmosis, neosporosis and
equine protozoal myeloencephalitis has saved billions of dollars worldwide in
healthcare and livestock production costs.
David L. Suarez and team members with ARS Southeast Poultry
Research Laboratory in Athens, Ga., were recognized at the
58th Annual Secretary's
Honor Awards Ceremony held in the Ronald Reagan International Trade Center
in Washington, D.C. They received the prestigious award for developing and
implementing rapid diagnostic tests, vaccine evaluation and policy development
to control an exotic Newcastle disease outbreak in the United States.
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